1. Field of the Invention
The present invention generally relates to method and apparatus for cleaning a semiconductor wafer, and more particularly, an embodiment of the invention relates to a brush assembly for removing slurry particles from a semiconductor wafer.
2. Description of the Related Art
Integrated circuit fabrication typically includes a process step of creating an extremely flat surface on a surface of a semiconductor wafer. Chemical-Mechanical Polishing (CMP) is a known technique for planarizing the surface of a semiconductor wafer to a desired thickness. CMP typically involves contacting a polishing pad against the wafer and rotating the polishing pad with respect to the wafer. A slurry containing abrasive particles is typically applied to the surface of the wafer to facilitate mechanical polishing of the wafer. The slurry may also contain a chemical agent to increase the rate that material is removed from the wafer. After the wafer is treated in a CMP process, it may be scrubbed to clean the wafer surface of any remaining slurry particles. The wafer may be contacted with water to remove the slurry particles.
In one process, a brush assembly that includes a brush attached to a brush holder is used to clean a semiconductor wafer after a CMP process. The brush includes a backing plate comprising a plurality of holes disposed about the edges of the backing plate. The brush includes a surface for contacting the wafer located on a side opposite the backing plate. Water is passed through the openings in the backing plate to the portion of the brush that contacts the wafer surface during cleaning. The brush is connected to the brush holder via a double-sided adhesive coupon placed between the backing plate and the brush holder.
The brushes used in the above-described system need to be periodically replaced. Such replacement tends to be difficult and time-consuming. The old brush and the adhesive coupon must first be removed from the brush holder. Removal of adhesive residue left by the adhesive coupon tends to be difficult, and acetone or another chemical often must be applied to the brush holder to facilitate removal of the adhesive residue. Once the old brush and adhesive coupon are removed, a new double-sided adhesive coupon is placed on the brush holder. Backing paper usually must be peeled from both sides of the adhesive coupon to expose its adhesive surfaces. Occasionally, the adhesive coupon tears when the backing paper is peeled away. The adhesive coupon contains a number of openings arranged to match a pattern of openings on the brush holder and the backing plate of the brush, It tends to be difficult to position the adhesive coupon on the backing plate and/or the brush holder such that the openings in the backing plate, brush holder, and adhesive coupon are properly aligned. In addition, the adhesive coupon may be incompatible with cleaning agents (e.g., ammonium hydroxide) that reduce or eliminate the adhesive capability of the adhesive coupon.
The brushes are typically replaced by operators who must wear latex gloves, which increases the difficulty and time required to: (a) remove the backing paper from the adhesive coupon without tearing the coupon, and (b) properly position the adhesive coupon on both the backing plate and the brush holder such that the patterns of openings are aligned in each of the three components. An operator typically spends about 2-4 hours to replace 6 of the brushes.
It is therefore desirable that an improved brush assembly be derived for cleaning a semiconductor wafer.